Conventional apparatus for attachment of plastic closure fitments typically employ in-line pairs of heated rollers arranged for receiving carton blanks therebetween and applying heat and pressure to the fitment and an extrusion layer on the carton blank at a point of tangential contact between the opposed surfaces of the rollers. Sealing rollers such as these do not apply heat and pressure to the fitment and extrusion layer combination when they are not in contact therewith. The extrusion layer is made of a heat-sealable material which is intended to form a thermal bond upon application of heat and pressure. Thus, in a conventional in-line apparatus, if the fitment does not immediately engage the extrusion layer, there is a possibility that the adhesive bond between the fitment and the extrusion may be defectively formed.
Additional rollers can be employed to provide successive applications of heat and pressure to the fitment and extrusion combination to ensure that a sufficient bond is formed. However, the additional rollers add length to the line, increase the cost of line operation and maintenance, and also increase the possibility of line breakdown. Alternatively, it has been recognized that intermittent motion type machines can supply heat and pressure for longer periods of time, but these machines heretofore have not proved satisfactory because they do not accommodate continuous feeding in high speed production. In these machines, a conventional bench type sealing apparatus can be employed to achieve fitment-to-extrusion adhesion wherein a carton blank and associated fitment are removed from a conveyor and appropriate heat and pressure are applied to the combination until the desired seal or adhesion is achieved. The finished blank is then returned to the conveyor which in turn is incremented, and the process is repeated again for the next fitment and carton.
The assignee of the present invention has developed low-profile plastic pour spout fitments which may be provided in a die-cut web for application to carton blanks by heat sealing processes. Each fitment is configured to form a pour spout upon removal from the web and attachment to a carton blank. Exemplary fitment configurations within the scope of this technology can be found in U.S. Pat. Nos. 4,705,197 and 4,770,325, both to Gordon and Kalberer, the disclosures of which are incorporated herein by reference.
The assignee has also developed an indexing apparatus which effects precise registration of fitments in die-cut openings within carton blanks. An example of this apparatus is disclosed in commonly-owned U.S. patent application Ser. No. 165,647, filed Mar. 8, 1988, in the names of Keeler, Bombolevich, and Sinocchi. Another example of an apparatus for the continuous application and sealing of die-cut fitments, such as plastic pour spouts, to carton blanks on a continuous conveyor line is disclosed in commonly-owned U.S. patent application Ser. No. 304,990, filed Feb. 1, 1989, in the names of Keeler and Bombolevich. The disclosures of these applications are also incorporated herein by reference.
However, there remains a need in the art for a high-speed sealing apparatus capable of synchronously interfacing with a high-speed continuous conveyor line to provide efficient and reliable fitment-to-extrusion adhesion using heated members. The apparatus should be useable with conventional carton blanks and fitments to ensure direct interface with existing types of production lines and, ultimately, consumer product acceptance.